Reach the upper factory route
Use the Warehouse’s upper route and a Robomb to clear the obstruction. In the Clockmaker’s Chambers, pull the rug and turn the revealed mechanism until the clock reads 9:00. Capture the awakened ghost for the ruby; this particular gem is available in C-3. Cross the Roundhouse beams and enter the Transportation Hall. Clear the Finishing Room encounter before using the Container Yard. Add activated Robombs to the weight mechanism until it lowers the bridge, then clear the next route without standing beside an exploding bomb.
Clear the Kiln Room and defeat the Ancient Poltergeist
In the Kiln Room, close the visible steam valve, restore the missing valve with Dark-Light and close that one too. Vacuum the remaining steam and flash the switch. Defeat the two Greenies in the compartment to expose the Boo. Continue through the upper Transportation Hall, uncover the key painting and extract the key with Dark-Light. Unlock the lower Roundhouse route for the Ancient Poltergeist. Dodge its bombs and sand attacks, then flash when it is exposed and vacuum it. Clear the following Sneakers and take the recovered clock hand. The clock puzzle at the bedroom is a collectible detour, not the way to damage this boss.
Collectible checklist
Old Clockworks gems — #7 Clockmaker’s Chambers
Boo checklist — Kiln Room: Close both steam valves, restoring the missing right one first. Vacuum the steam, flash the switch and catch the two Greenies in the compartment.